The HURD was meant to be the true kernel at the heart of the GNU operating system. The promise behind the HURD was revolutionary -- a set of daemons on top of a microkernel that was intended to surpass the performance of the monolithic kernels of traditional Unix systems and in doing so, give greater security, freedom and flexibility to the users -- but it has yet to come down to earth.

I generally agree. Chasing ever-better kernels is a clear mistake. Whatever works best *right now* should be used, and to hell with the negatives. Once you have a fairly complete system you can revisit the question of whether replacing the kernel is worthwhile. If it still sounds good then, do it.